Emissions regulations in many areas of the world have introduced the need to utilize aftertreatment systems for internal combustion engines. An exemplary system uses a diesel exhaust fluid (DEF) such as a urea-water solution injected into the engine exhaust stream. In the presence of a properly selected catalyst, the DEF reacts with NOx in the exhaust stream, eliminating a portion of the NOx through reduction. The use of DEF is effective for reducing NOx, but suffers from several drawbacks. The DEF can freeze in cold ambient environments, causing a long delay period after engine startup until the aftertreatment system is fully functioning to reduce emissions. The DEF fluid must be atomized in the exhaust fluid into very small droplets to support evaporation of the DEF, and to further support decomposition of urea into ammonia, where applicable. Certain systems to ensure atomization include air-assist devices in the DEF injection system. A properly designed air-assist device is effective in ensuring the DEF is fully atomized in the exhaust stream. However, contact between the air and the DEF, especially where fluid temperatures are low, can cause crystallization of components of the DEF on injectors, in flow tubes, or in other areas of the system that cause sub-optimal performance or system failure. Where crystallization of components of the DEF occurs, it can be a challenge to detect and treat the crystallization condition without performing a full service event.